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Nothing is quite like bringing a brand-new human being into the world, unless you’re bringing two brand-new human beings into the world, that is. The wonder of twins certainly doesn't end at birth, though. Whether they’re identical or fraternal, here’s just a small sampling of facts about your precious pair.

They bond before they’re born: Three-dimensional ultrasound images of twins in utero have shown that the fetuses seem to reach for each other intentionally and (aw!) stroke each other as early as 18 weeks. If you've got multiples, try to remember their prenatal chumminess the next time they’re tearing each other’s hair out. Yes, twins fight — but they also seem to be hardwired to connect.

They talk in tongues! About 40 percent of twins actually develop their own language, according to researchers — and it’s not just baby babble either. Twins often look to each other as language models and assign meaning to those jabbers. So, “pfft!” could mean “let’s go!” to your tiny twosome. Don’t worry, their twin-speak won’t hinder their actual language development (most twins drop the secret speech as their real vocabulary expands), but it sure is cute while it lasts!

They may yawn contagiously with each other: Contagious yawning (when you see someone else yawn and you reflexively feel the need to do the same yourself) may not seem like a big deal. Except that most kids typically don’t exhibit this behavior until they’re about five years old, when the part of the brain that controls empathy starts to mature. True, babies yawn a lot in general, so it could be coincidental. But there’s also a good chance all that in-utero bonding has created an empathic connection that causes your mini duo to share in their own special yawn sessions.

They have differences, even if they are identical: Can’t tell a pair of identical twins apart? Print ’em! Despite having matching DNA, the pattern of skin grooves and ridges on their fingers is not the same. Fingerprints are believed to be affected by each baby’s bone growth and contact with amniotic fluid in utero — so while they’re likely very similar, their fingerprints will never be exactly the same (unlike, say, their cowlick or dimples).

They affect each other’s sleep for years: When they’re babies, their middle-of-the-night hunger cries will wake each other up (and even if they don’t, you’ll probably rouse the sleeping twin when the other wakes up to eat). As toddlers, they’ll giggle at each other through the bars of their cribs, shaking the rails and flopping on their mattresses hysterically. Oh, you’ll put them in separate rooms, you say? Good luck with that. Either one twin will be too scared to sleep alone or will refuse to fall asleep until they see the other twin is sleeping too — which means nonstop room-hopping until you give up and put them back together again. As older kids, even if one twin is bone-tired she likely won’t go to bed if the other one is awake, because she doesn't want to miss out on anything her twin may be experiencing. The upside: Parents with kids of different ages have to plan their days around multiple nap schedules and bedtimes, so having two on the same sleep routine is one of the few ways twins can be easier!